How can scientists test their ideas about the origin of the universe if they can't physically interact with or study it? i tried the answer "b." and that's not the right answer i guess.
a. the cosmological principle makes assumptions that provide scientific guidelines to enable its study.

b. physicists develop mathematical equations to determine its physical nature.

c. the big bang theory provides the scientific guidelines to enable its study.

d. scientists are able to gather samples from nasa.